Isotopes used for radiological dating
The unstable isotopes change over time into more stable isotopes, in a process called radioactive decay.
The original unstable isotope is called the parent isotope, and the more stable form is called the daughter isotope.
Another example is luminescence dating, which measures the energy from radioactive decay that is trapped inside nearby crystals.
For humans, the steady movement of the hands on a clock marks off the seconds and the hours.
When ‘parent’ uranium-238 decays, for example, it produces subatomic particles, energy and ‘daughter’ lead-206.
Isotopes are important to geologists because each radioactive element decays at a constant rate, which is unique to that element.
These rates of decay are known, so if you can measure the proportion of parent and daughter isotopes in rocks now, you can calculate when the rocks were formed.
One half-life is the time it takes for ½ of the parent isotopes present in a rock or bone or shell to decay to daughter isotopes.Parent isotopes decay to daughter isotopes at a steady, exponential rate that is constant for each pair.The shape of this curve is the same for the radioactive decay of all isotopes.This is different to relative dating, which only puts geological events in time Most absolute dates for rocks are obtained with radiometric methods.These use radioactive minerals in rocks as geological clocks.